They have been skating __________.
#40389
A
for three hours
B
since three hours ago
C
three hours ago
D
since three hours
推荐题目
I will _______ him when I _______free.
#41766
A
call, am  
B
call to, am
C
call, will be 
D
call to, will be
I ________some chickens in the countryside yesterday.
#39288
A
feed
B
feeds
C
fed
D
feeding